Method of making non-rigid rotative abrasive structures



July 4, 1961 V, MEYER ETAL 2,991,165

United States Patent,

2,991,165 METHOD '0F MAKING NON-RIGID ROTATIVE ABRASIVE STRUCTURES Vincent Meyer, South St. Paul, 'and Howard F. Payer, St. Paul, Minn., assignors to Minnesota Miningand Manufacturing Company, St. Paul, Minn., a corporation of Delaware v Filed Jan. 2'4, 1958, Ser. No. 710,838 6 Claims. (Cl. 51293) The present invention relates to new and improved methods of manufacturing non-rigid rotative abrasive structures of the nature of those described and claimed in copending Miller and Gothier application Serial No. 545,390, tiled November 7, 1955, now abandoned. More particularly the present invention is concerned with novel and advantageous methods of forming abrasive flap wheel structures, which structures are comprised of an annulus of many juxtaposed radially extending flap sections of abrasive sheet material, wherein adjacent flap sections `are rigidiiied and iirmly rigidly adhesively bonded together over a substantial radially inner end area to form a rigid reinforced inner rim portion in said structures all across the width thereof.

Abrasive ilap wheels of the nature of those vdescribed in Miller and Gothier application Serial No. 545,390 can be manufactured by arranging many identically shaped flap sections of abrasive sheet material in superposed face-to-back relation so as to form a block or pack of said flap sections. The flap sections can have a pair of opposed notches in the lateral edges adjacent the ends thereof which are bound together, these notches aligning in the block of ilaps to define opposed lateral grooves therein.

In the method specifically described in said Miller and Gothier application Serial No. 545,390, the block of notched tlaps is bound together for manipulation into the annulus by applying one or more narrow flexible adhesive coated strips 4lengthwise along the surface of the block ydefined by the ends of the flap sections 4which will form the inner periphery of the annulus, the surface to which the said tape is applied being first primed with the aid of a primer adhesive. The said strips cover only a portion Width-wise of the block surface to which they adhere. Liquid curable adhesive is then applied to the remaining exposed area of the taped surface therebyA to coat the individual tlap sections adjacent the taped block surface. The block is then manipulated into an annulus. Then forming rings are inserted in place in the lateral grooves defined by the aligned notches, following which the tape strips are removed. Additional liquid curable adhesive is applied after removal of the tape strips, inter alia, by painting the inner periphery of the annulus several times with said adhesive. Although this method is operable in all respects to provide the desired abrasive flap wheel structure, it involves numerous procedural steps and tends to be somewhat cumbersome and disadvantageous from the aspects of commercial manufacture. Further, the presence of the primer adhesive and 4any residuum of adhesive from the tape strips tends to inhibit the uniform incorporation of liquid curable adhesive into the annulus from the inner peripheral surface.

It is an object of the present invention to provide a novel method involving a minimum number of procedural steps and suitable for the ecient commercial manufacture of abrasive iiap wheel structures. A further object is to provide a novel method of making abrasive Hap wheel structures wherein an assembled block of super# rice block of superposed abrasive ap sections can be manipulated into an annulus Without necessityV of prior application 'of adhesive resin, or adhered tape strips. An additional specic object is to provide a commercially practical mode of manufacturing abrasive flap Wheels wherein uniform distribution of liquid curable binder adhesive in a tlap wheel annulus is attained in a single application' step.

The manner in which these and other objects and ad-f vantages are achieved will be apparent from the following detailed description of our invention, and from the appended drawing wherein like reference characters referv to corresponding parts in the several views, and in whiclu'r FIGURE 4 is a vertical section view of the annulusV of flap sections with annular side flanges in place, this view also being at an intermediate stage of manufacture; and

FIGURE 5 is a view, somewhat schematic in character, showing the structure of FIGURE 4 mounted for rotation duringsubsequent manufacturing procedures.

Flap sections 10 of sheet material, for example including flexible coated abrasive sheet material, are die-cut or otherwise formed to identical generally rectangular shape, each ap section having a single pair of opposed notches 1\1 and 11a in the lateral edges of the flap sections adjacent one end thereof. The Hap sections may take generally the shape of those described and shown in the drawing of said Miller and Gothier application Serial No. 545,390 except that the flaps contain only a single notch in each lateral edge (although, of course, if desired two or more notches can be utilized in each lateral edge). The said flap sections are then assembled in superposed face-toback relation into a block or pack 12, with the notches in the Hap sections aligning in the block to define opposed grooves 13 and 13a in the lateral surfaces thereof. T he block 12 of flap sections is then pressed in the longitudinal `direction to provide a dense distribution of flaps, a typical pressure being about 35 pounds per square inch. (The block or pack of flaps is so compressed that the portion thereof containing the later-al grooves is exposed and accessible, for example the flaps can be assembled and compressed in an elongate channel member posed liaps is simply and easily bound together by stretchhaving a U-shaped cross section with the ends of the flaps containing the notches extending upwardly land out of the channel.

An elastic member 14 of continuous length, e.g., a conventional so-called rubber binder, of suitable length is stretched over and about the periphery of the block, generally in a plane perpendicular to the ap sections. The elastic member is then released so as to nestle tautly in place along and within each of the lateral grooves 13 and 13a and about the exposed surface of the ap section at each end of the block 12. Thereby the block is unified temporarily. Then, with the ends of the ap sections adjacent'the said notches forming the inner periphery, the block of aps is manipulated into an annulus with the Hap section at each end of the block being brought into faceto-back Aabutting relationship. This manipulation may in? volve somewhat of a dexterous trick; Ibut it will be observed, n connection with FIGURE 3, that if the ends of the block are grasped with the hands, without immediate concern for the mid-portion of the block, and if said ends then are quickly brought around toward one another in a generally circular arc the annulus lis formed without mishap. 'I'he forming operation is conveniently conducted perspective of a block of Superf with the block of aps lying on its side on a flat supporting surface.

An annular side ange having a center hole of lesser diameter than the inner diameter of the flap wheel annulus just formed, and further having a laterally extending ring 16 adjacent the outer periphery thereof of such size as to coincide with the now circular lateral groove 13 in the flap wheel annulus, is then driven lightly into position with said lateral ring partially extending into said circular groove. The elastic member is cut free from the groove at the opposite surface of the ilap wheel. With care being taken not to disrupt the packed annular relationship of the aps, the elastic member is pulled free of the annulus. Since the side flange was only driven lightly into place, the binder will pull free of the groove into which the side flange was inserted. A second flange 15a, like the first, is then firmly driven into position in the lateral surface of the wheel opposite that retaining the rst flange, with the laterally extending ring 16a extending within now circular lateral groove 13a. Following this it may be advisable to invert the wheel and again drive the rst applied flange so that the lateral ring of the latter will set more deeply into the groove now free of the elastic member. The anges serve to retain the radially extending flap sections firmly in uniform densely packed relation at the inner peripheral portion of the annulus pending incorporation of the resinous adhesive material between the aps.

As schematically shown in FIGURE 5, the tlap annulus is then mounted for rotation on a horizontal axis, the speed of rotation preferably being controlled through a motor 17 containing a variable speed drive mechanism 18. Mounting is such that the center hole of one of the side flanges is accessible for the flowing or pouring of adhesive into the central portion of the tiap wheel. For example, the flap wheel annulus can be clamped from one side in a horizontally rotatable jaw mechanism which grips the peripheral portions of the flap wheel side anges thereby retaining the flap wheel on a horizontal axis while leaving the center portion of one ange accessible.

The annulus is rotated, and during such rotation the liquid curable adhesive resin is added, for example through a pour tube 19, Vthrough the center hole of the annular side flange into the space in the center of the flap Wheel defined therebetween. The liquid resin thus flows onto the inner periphery of the abrasive annulus temporarily forming a pool at the lower portion of the cavity defined by the inner peripheral portion of the annulus and the side flanges. Rotation is at a speed sutlicient for centrifugal forces to cause the liquid resin to flow or seep radially outwardly between the wheel flaps. In this fashion the flow of the liquid resin radially outwardly will be uniform all about the inner circumference. Rotation at the initial rate is continued at least until most or all of the resin pool has disappeared. The speed and the duration of rotation should be so limited that the resin is retained at the inner peripheral portion of the abrasive annulus rather than being thrown to the outer portion of the annulus. Preferably the speed of rotation is then reduced to a rate at which the resin no longer is forced radially outwardly between the flaps, rotation at this slower speed continuing until the adhesive resin has cured to at least a non-owable state.

Heat may be advantageously applied to facilitate the cure-time of the resin and to improve physical characteristics of the thus cured adhesive. This heat source may be employed in the form of a cartridge heater of suitable diameter, the heater being inserted through the center hole between flanges into the cavity.

Following the cure of the resin adhesive the Wheel structure is demounted and the side flanges removed, at which time the resulting structure is ready for mounting on a hub or shaft (e.g., with the aid of side flanges) to be used in abrading operations. If desired, the side flanges employed in the manufacture may be of such configuration and design as to be mountable with the ap wheel on a drive shaft. In this instance the flanges need not be removed at the end of the manufacturing procedures, the wheel instead being used or sold with the flanges remaining attached.

In order to facilitate the practice of the method just described, and to assist in the proper determination of rotational speeds, time of rotation, etc., the following specie illustration will be helpful: An abrasive annulus composed of 160 generally rectangular flaps of a size of about 2% inches by 2 inches was formed by incorporating a conventional rubber binder around and about a block formed of said flaps all in the manner above described. The flaps were composed of grit abrasive mineral adherently coated on a treated `drills cloth backing (Resinbond Three-M-Ite cloth available from Minnesota Mining and Manufacturing Company, St. Paul, Minnesota). When manipulated into an annulus the ap wheel structure had an outer diameter of 6 inches, an inner diameter of 1% inches and a width of 2 inches. The annulus was rotatably mounted and then rotated at a speed of about 140 r.p.m. One and one-half ounces of curable liquid epoxide-type resin adhesive, like that described in connection with the previous example (diethylene triamine accelerated Bakelite BR-l8774), were added to the inner periphery of the flap wheel through the center hole in one side flange. Following the addition of the resin a threefourth inch diameter 700 F. cartridge heater was inserted into the cavity between the side flanges. Rotation at the initial rate was continued for about a minute and a half following completion of the addition of the resin adhesive. Rotational speed was then decreased to vabout 24 r.p.m., and rotation at this slower speed was continued for approximately 31/2 additional minutes. By this time the adhesive resin had cured to a rigiditied state thereby to provide a rigidly reinforced inner rim in the annulus. Following this the structure was demounted from the rotating mechanism and allowed to cool.

The rotational speed, time of rotation, etc. employed in the case of the specific wheel just described may or may not be the optimum values for the manufacture of ap wheels of different size, different numbers or types of abrasive flaps, different adhesive resins, etc. For general guidance, however, it may be stated that where an adhesiveV resin more thinly fluid than that employed in the specific example is employed, the initial rotational speed utilized generally will be less than that shown. On the other hand where a viscous resin is employed the rotative speed will be greater since such viscous resin is less affected generally by centrifugal force of given magnitude than is a more thinly tluid resin. Similarly, where thc abrasive of the flap sections is of a tine grade, such that the interstices between the abrasive particles and between adjacent flap sections are relatively small, ya greater rotational speed will be required to cause proper distribution of adhesive resin than where the tlap sections contain a coarse abrasive material. Also, a longer period of rotation at the ygreater rotative speed may be required in the case of a more viscous adhesive resin or in the case of a ne `abrasive grit-size than where a more thinly uid resin or a coarse abrasive grit-size is utilized. Time of rotation at the nal (i.e., slower) rotative speed largely will be governed by the curing time of the resin, a shorter time generally being required in the instance of a rapidly curing material than in the case of a slowly curing resin. These principles are presented as a general indication of the direction to proceed in experimentally determining optimum conditions for a given specific case. It should bc borne in mind, of course, that individual peculariti of the specific materials employed may affect or tend to override the above principles and thus must be considered.

Commercially the procedures described herein have found most extensive use in the manufacture of wheel structures of small and medium diameter, up to about l1 inches in diameter, but inherently has characteristics which render it attractive for preparing larger wheels. It can be used for making wide wheels as well as narrow wheels.

Various modifications of the procedures described herein undoubtedly suggest themselves, but it is to be understood that the specific example has been presented 'for the purpose of illustration, not for purposes of limitation, and that the scope of the invention is intended to be limited only by the disclosure as a whole, including the appended claims.

We claim:

l. In the method of forming an abrasive liap wheel wherein adjacent fiap sections are rigidified and firmly ridigly adhesively bonded together over a substantial radially inner end area to -forrn a rigid reinforced inner rim portion in said structure, the steps comprising forming a block of superimposed abrasive sheet flap sections, each flap section having at least one pair of opposed notches in the lateral edges adjacent one end thereof with said notches 'aligning to define opposed grooves in the lateral surfaces of said block, applying flexible stretchable bind ing means about said block with said binding means extending in and along each of said grooves thereby to unify the block, manipulating said unied block into an annulus with said one end of said flap sections `forming the inner periphery thereof, inserting a circular forming member into a groove in each of said lateral surfaces to perfect the shape of said annulus, said sections each being provided ywith a coating of a liquid curable adhesive on each side thereof over a substantial area adjacent said ends, and curing said adhesive to a rigid hard firm state.

2. In the method of lforming an abrasive fiap wheel wherein adjacent flap sections are rigidified and firmly rigidly adhesively bonded together over a substantial radially inner end area to form a rigid reinforced inner rim portion in said structure, the steps comprising forming a block of superimposed abrasive sheet flap sections, each flap section having at least one pair of opposed notches in the lateral edges adjacent one end thereof with said notches aligning to define opposed grooves in the lateral surfaces of said block, applying tiexible stretchable binding means about said block with said binding means extending in and along each of said grooves thereby to unify the block, manipulating said unified block into an annulus with said one end `of said flap sections forming the inner periphery thereof, inserting a circular forming member into a groove in each of said lateral surfaces to perfect the shape of said annulus, incorporating liquid curable adhesive between each of said flap sections to provide essentially a complete coating of said adhesive on each side of said sections over a substantial area adjacent said ends, and curing said ad hesive to a rigid hard firm state.

3. In the method of forming an abrasive flap wheel wherein adjacent flap sections are rigidied and firmly rigidly adhesively bonded together over a substantial radially inner end area to form a rigid reinforced inner rim portion in said structure, the steps comprising forming a block of superimposed abrasive sheet iiap sections, each flap section having at least one pair of opposed notches in the lateral edges adjacent one end thereof with said notches aligning to dene opposed grooves in the lateral surfaces of said block, applying fiexible stretchable binding means about said block With said binding means extending in and along each of said grooves thereby to unify the block, manipulating said unified block into an annulus with said one Yend of said flap sections forming the inner periphery thereof by grasping the opposite end portions of said block and quickly bringing them around in a generally circular path toward one another until the flap sections on each end come into abutting juxtaposed relationship, incorporating liquid curable adhesive between each of said -liap sections to provide essentially a complete coating of said adhesive on each side of said sections over a substantial area adjacent said ends, and curing said adhesive to a n'sid hard firm state 4. In the method of forming an abrasive fiap wheel wherein adjacent flap sections are rigidified and firmly rigidly adhesively bonded together over a substantial radially inner end area to form a rigid reinforced inner rim portion in said structure, the steps comprising forming a block of superimposed abrasive sheet flap sections, each fiap section having at least one pair of opposed notches in the lateral edges adjacent one end thereof with said notches aligning to define opposed grooves in the lateral surfaces of said block, applying a fiexible stretchable rubber-like binder of continuous length about said block with said binder extending in and along each of said grooves thereby to unify the block, manipulating said unified block into an annulus with said one end of said flap sections forming the inner periphery thereof, insert ing a circular forming member into a groove in each of said lateral surfaces to perfect the shape of said annulus, rotating said annulus and adding liquid curable adhesive to the inner peripheral portion thereof thereby utilizing centrifugal force to incorporate said adhesive between each of said iap sections to provide essentially a cornplete coating of said adhesive on each side of said sections over a substantial area adjacent said ends, and curing said adhesive to a rigid hard firm state.

5. In the method of forming an abrasive flap wheel wherein adjacent flap sections are rigidified and firmly rigidly adhesively bonded together over a substantial radially inner end area to form a rigid reinforced inner rim portion in said structure, the steps comprising forming a block of superimposed abrasive sheet fiap sections, each flap section having at least one pair of opposed notches in the lateral edges adjacent one end thereof with said notches aligning to define opposed grooves in the lateral surfaces of said block, applying a flexible stretchable rubber-like binder of continuous length about said block with said binder extending tn and along each of said grooves thereby to unify the block, manipulating said unified block into an annulus with said one end of said fiap sections forming the inner periphery thereof by grasping the opposite end portions of said block and quickly bringing them around in a generally circular path toward one another until the fiap sections on each end come into abutting juxtaposed relationship, incorporating liquid curable adhesive between each of said .Hap sections to provide essentially a complete coating of said adhesive on each side of said sections over a substantial area adjacent said ends, and curing said adhesive to a rigid hard firm state.

6. In the method of forming an abrasive ap wheel wherein adjacent flap sections are rigidified and firmly rigidly adhesively bonded together over a substantial radially inner end area to form a rigid reinforced inner rim portion in said structure, the steps comprising forming a block of superimposed abrasive sheet iiap sections, each flap section having at least one pair of opposed notches in the lateral edges adjacent one end thereof with said notches aligning to define opposed grooves in the lateral surfaces of said block, applying flexible stretchable binding means about said block with said binding means extending in and along each of said grooves there by to unify the block, and manipulating said unified block into an annulus with said one end of said ap sections forming the inner periphery thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,678,523 Leggett May 18, 1954 2,749,224 Block June 5, 1956 2,796,337 Block June 18, 1957 2,818,692 Bernstein Jan. 7, 1958 

1. IN THE METHOD OF FORMING AN ABRASIVE FLAP WHEEL WHEREIN ADJACENT FLAP SECTIONS ARE RIGIDIFIED AND FIRMLY RIGIDLY ADHESIVELY BONDED TOGETHER OVER A SUBSTANTIAL RADIALLY INNER END AREA TO FORM A RIGID REINFORCED INNER RIM PORTION IN SAID STRUCTURE, THE STEPS COMPRISING FORMING A BLOCK OF SUPERIMPOSED ABRASIVE SHEET FLAP SECTIONS, EACH FLAP SECTION HAVING AT LEAST ONE PAIR OF OPPOSED NOTCHES IN THE LATERAL EDGES ADJACENT ONE END THEREOF WITH SAID NOTCHES ALIGNING TO DEFINE OPPOSED GROOVES IN THE LATERAL SURFACES OF SAID BLOCK, APPLYING FLEXIBLE STRETCHABLE BINDING MEANS ABOUT SAID BLOCK WITH SAID BINDING MEANS EXTENDING IN AND ALONG EACH OF SAID GROOVES THEREBY TO UNIFY THE BLOCK, MANIPULATING SAID UNIFIED BLOCK INTO AN ANNULUS WITH SAID ONE END OF SAID FLAP SECTIONS FORMING THE INNER PERIPHERY THEREOF, INSERTING A CIRCULAR FORMING MEMBER INTO A GROOVE IN EACH OF SAID LATERAL SURFACES TO PERFECT THE SHAPE OF SAID ANNULUS, SAID SECTIONS EACH BEING PROVIDED WITH A COATING OF A LIQUID CURABLE ADHESIVE ON EACH SIDE THEREOF OVER A SUBSTANTIAL AREA ADJACENT SAID ENDS, AND CURING SAID ADHESIVE TO A RIGID HARD FIRM STATE. 